1. Field of the Invention
The invention relates to a safety switching apparatus comprising a case, an electric switch adapted to be actuated by a longitudinally mobile pusher when one end thereof, extending into a transverse window of the case, receives a movement which is communicated thereto by rotary transmission means cooperating with a key introduced transversely in this window and such that this movement cannot be communicated thereto in the absence of the key.
2. Description of the Prior Art
Such a switching apparatus, which is for example used in safety circuits where the state of the switch must only be able to be modified by the position of a door, in which this key is placed, is known more particularly from French patent No. 2 498 004.
In this known apparatus, it may be feared that the key, which is formed by a metal wire loop, may be subject to accidental deformations which may make the subsequent operation thereof difficult.
In addition, the use of a rotary member, which has a symmetrical trend so as to make actuation possible in one of several directions, means that the pusher cannot be given a substantial stroke unless very sloping cam surfaces are provided on this member, which could cause undesirable friction, even jamming. Finally, the very shape of the key does not guarantee that an unauthorized person may actuate the switch with a means equivalent to this key.